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Vintage diode identification

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What current rating is the fuse F1?

Figured out that smallest axial avalanche diode body is SOD-57 with the wire diameter 0.82mm that is a bit thicker than my original with 0.6mm.
Here is the list with plenty of them (SOD-57). If I should get some for the tests what would be your suggestions for Vr/Io/Vf?


--- Quote from: wasedadoc on August 11, 2022, 06:44:25 pm ---What current rating is the fuse F1?

--- End quote ---

I would not rely on that fuse rating because it is obviously put in some time before I've got this machine and after it was sold. It has two post factory repairs (one old style reed relay changed to little bit newer type and this fuse).  It is not an initial factory circuit setup. Whoever put that fuse into the circuit meant to protect DC bridge and DC wire supply motor from variable transformer AC supply (current sensing transformer that adjusts motor speed with the welding current). The fuse has marking T4/250D that seems to be 4 amp fuse.

However there are original 4 fuses @ 2 amps on machine case. No doubt that they are meant to be 2amps because they all have clear factory marks on dashboard. One I see is for magnetic power switch (switches welding transformer to the 3phase mains) that is controlled by my control circuit. The others are hard to trace right now. Wire feed DC motor has following markings on its case - 39V, 52W and might be 1.9A (the amp reading is hard to see - have to look through mirror, but definitely below 2amps, 1.something). So that leads to 2amps all in all and 4amp fuse seems to be wrong choice here.


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